They are trying to control how she handles this because she has shown that she is unable to make the right choices on her own.
Teenage pregnancy. No contact with the father, so he obviously wasnt a good guy. Straight into an abusive relationship with another not great guy. Wont stop contact with him. Gets belligerent when they try to help. Considers leaving a refuge and shouts at them.
She isnt capable of making the right choices. She cant go home and live with you because you've also ended up homeless with kids and no father around?
This is blunt, and cruel, but it is what SS are seeing. You could be wonderful; the most loving mum and attentive grandparent. But look at what SS is seeing. A teenage pregnancy, quickly moving to a new man, continuing contact once his violent nature is exposed without a care for what that will do to her child and no stable home life to go back to, no suitable family home to return to.
Given everything that's happened with his pandemic, many people have found themselves homeless. It very well may not be your fault, but that doesnt make the reality of the situation any different.
If your daughter wont listen, what else do you expect from SS when you really consider what they are seeing.
Maybe the best thing you can do is work with them as much as possible to ensure you can get visits with the child, and if you can get yourself into a stable living situation then you can try to have him placed with you.